Diabetes mellitus is a group of diseases characterized by abnormalities in the function and structure of tissues and organs due to high blood glucose levels. The disease state should be diagnosed when tissue and organ damage occurs, which is too late. It is reasonable to use the characteristic lesions triggered by blood glucose to make a diagnosis. However, since blood glucose is a continuous variable, it is not reasonable to use a single blood glucose level as a diagnostic cut-off point for the disease. Therefore, the diagnostic criterion for diabetes mellitus is established as a relative level, i.e., the point above which the characteristic hyperglycemic lesion caused by the glycemic state begins to show a statistically significant increase. In populations, the cut-off point for blood glucose levels can vary to some degree across the population depending on factors such as ethnicity, age, gender, and living environment. The cut-off point between normal and abnormally hyperglycemic states is artificially defined, but is critical for clinical management. The cut-off point for the diagnosis of diabetes mellitus is based primarily on the effect of blood glucose on retinopathy. At the same time, health economics, population tolerance to the concept of the disease, etc., are taken into account, as well as the need for prevention and treatment of diabetes mellitus and its complications. The diagnostic criteria for hyperglycemia in diabetes mellitus are based on the value of hyperglycemia that causes damage to the microvessels, not on the value of blood glucose at which diabetes mellitus becomes symptomatic. Incomplete blood glucose testing leads to a high rate of underdiagnosis of diabetes. If the origin of the diagnostic criteria for diabetes mellitus is not based on the symptoms of “three more and one less”, how many people with diabetes mellitus due to the absence of symptoms and hidden in the normal population? 1986 Daqing Diabetes Survey in China and the results of the National Diabetes Prevalence Survey in 1994 showed that newly diagnosed diabetes mellitus accounted for 70% of the total number of diabetes mellitus, that is, the rate of underdiagnosis of diabetes mellitus. That is to say, the under-diagnosis rate of diabetes is as high as 70%. This shows that early diabetes due to the lack of obvious symptoms and did not realize that the blood sugar has reached the stage of high blood sugar harmful to the body. Even in the diabetes surveys of developed countries, the underdiagnosis of diabetes is as high as about 50%. The gap between the symptoms of diabetes and the diagnostic criteria is the blood glucose level. Patients with “three more and one less” is a late symptom, with diabetes symptoms of blood glucose value and blood glucose control target value between the distance is too large, so you must monitor blood glucose in order to know its level. In clinical treatment, many patients are treated only on the basis of symptoms, losing time to chronic hyperglycemia without treatment, which is an extremely wrong approach. Many diabetic patients have gone through the process of not monitoring their blood glucose at an early stage and letting high blood glucose persist for a long period of time based on their self-perception; some patients, although they have good health care, just do not understand the meaning of glycemic control and fail to keep their blood glucose in a good range for a long period of time. Indicators of blood glucose monitoring and its significance Since mild to moderate hyperglycemia has no obvious symptoms, blood glucose monitoring is the only way to understand the blood glucose level. There are two main types of blood glucose monitoring indicators, those that represent long-term blood glucose and those that represent point blood glucose. The former includes glycosylated hemoglobin (HbA1c) and glycosylated serum protein, while the latter includes multi-point preprandial, postprandial and bedtime blood glucose. HbA1c HbA1c refers to the protein glycation product formed by blood glucose and hemoglobin in red blood cells. In adulthood, hemoglobin is predominantly HbA, accounting for 97% of the total, and the glycated fraction is called HbA1, with HbA1c representing the predominantly glycated HbA1 fraction. Since the lifespan of a red blood cell is 120 days, the formation of glycated hemoglobin represents the average lifespan of a red blood cell in the blood. If blood glucose levels do not fluctuate much, there is a good correlation between the average blood glucose and HbA1c levels over a period of about 3 months, representing roughly the average blood glucose level over the 2-3 months prior to measurement. However, the blood glucose of diabetic patients is unstable, and it was found that 50% of the HbA1c level was mainly the result of glycation of the average blood glucose in the month before the measurement, suggesting that the average blood glucose level in the last month has an important influence on the formation of glycated hemoglobin, which is helpful for the change of therapeutic drugs in clinical treatment. Among the other 50%, about 40% of the HbA1c was more related to the average blood glucose of 2~3 months before the measurement, and only 10% represented the average blood glucose level of 3~4 months. 1441 cases of type 1 diabetes mellitus provided a large number of data related to multipoint blood glucose, average blood glucose and HbA1c in the DCCT study, and the correlation between HbA1c and average blood glucose was very good, and the relationship between the two was calculated by the statistical calculation. The correlation between HbA1c and average blood glucose is very good, and the relationship between the two is deduced through statistical calculations. The following table is provided for clinicians to use the simple HbA1c results to calculate the recent average blood glucose. Table Relationship between average blood glucose and HbA1c HbA1c MPG (plasma glucose) MPG (whole blood glucose) mg/dl(3) mg/dl & mmol/L(1,2) 4 65=3.5 mmol/L (60) 5 100=5.5 mmol/L (80) 6 135=7.5 mmol/L (120) 7 170=9.5 mmol/L (150) 8 205=11.5mmol/L (180) 9 240=13.5mmol/L (210) 10 275=15.5mmol/L (240) 11 310=17.5mmol/L (270) 12 345=19.5mmol/L (300) It can be memorized simply as follows: If the average blood glucose for a HbA1c=6% is 7.5mmol/L, the average blood glucose for a HbA1c=6% is 7.5%. If HbA1c=6% corresponds to an average blood glucose of about 7.5mmol/L, then for every 1% increase in HbA1c, the average blood glucose will increase by about 2mmol/L. HbA1c is now widely used for long-term blood glucose monitoring in diabetic patients, and it is the “gold standard” for both research on the effects of blood glucose on chronic complications and for judging the effects of various hypoglycemic drugs. It is a very good choice to measure HbA1c twice a year for those with stable condition and four times a year for those with unstable condition, while fasting and postprandial blood glucose can be used as substitutes for HbA1c in areas without such conditions. Glycated Serum Protein (GSP) When blood sugar fluctuates within the normal range, glucose also binds to a small amount of protein in the serum to form glycated serum protein. Serum proteins have an average lifespan of about 4 weeks and a half-life of 2 weeks, so GSP represents the average level of blood glucose over a 2-week period. It represents a more recent average blood glucose level than HbA1c, and can be more useful for treatment, but is not widely used in clinical practice because of the difficulty of measuring it. Spot blood glucose Spot blood glucose is not only a criterion for the diagnosis of diabetes, but also a good indicator to guide the use of medication in diabetes treatment. Since fasting and postprandial hyperglycemia are both clinical types of hyperglycemia, representing the sensitivity of different organs to insulin and the degree of hyperglycemia in different diabetes mellitus, they are both important for clinical use. Fasting blood glucose mainly represents the amount of hepatic gluconeogenesis and glycogen output and the ability of insulin to inhibit hepatic glycogen output. Since it is a non-meal state, it largely reflects endogenous pancreatic function in addition to hepatic insulin resistance. Most people with early diabetes and impaired glucose regulation have predominantly postprandial or post-glycemic hyperglycemia, with relatively low fasting glucose. Only about one-fourth of the population shows a simple increase in fasting glucose. In patients with advanced diabetes mellitus, there is a progressive decline in endogenous islet function. Fasting blood glucose also rises progressively, although the absolute value of postprandial blood glucose is very high with the increase of fasting blood glucose. The absolute value of postprandial blood glucose is very high with the increase of fasting blood glucose, but the value of increase is relatively fixed. Treatment of fasting and postprandial glucose needs to be individualized. Point blood glucose measurements can be self-monitored using a glucometer, which, due to its constant updating, correlates well with venous plasma glucose values, especially in the medium to high glucose region. The correlation is poorer in the very high or very low regions. Spot blood glucose is mainly used to adjust the dosage of therapeutic drugs, especially in patients using insulin; it is also a means of detecting hypoglycemia. It is also a means of detecting hypoglycemia, and can be compared with HbA1c through multi-point, long-term spot glucose monitoring. Generally speaking, for patients with stable blood glucose, spot blood glucose can be measured every 1~2 weeks for one day, and for those with unstable blood glucose, it can be measured according to the needs of the condition. The relationship between HbA1c and spot blood glucose Several years ago, when controversy arose over the importance of fasting and postprandial glucose in diabetic patients, it was mainly due to the finding that postprandial or postload hyperglycemia in a subset of the hyperglycemic population was associated with an increased risk of future cardiovascular events. Fasting blood glucose was not associated with the risk of future cardiovascular events in these populations, and control of postprandial hyperglycemia was therefore considered to be one of the most important aspects of the prevention and treatment of diabetic macrovascular disease. This conclusion is true in people with early diabetes or impaired glucose regulation, but it cannot be said that postprandial glucose treatment is the most important aspect in all diabetic populations, hence the argument about who is most important, fasting or postprandial glucose. Research from French scholar Monnier answered the relationship between HbA1c and point blood glucose, in 290 cases of diabetes, through the relationship between multi-point blood glucose testing and HbA1c, calculated that when HbA1c<7.3%, the postprandial glucose increase part of the contribution to the HbA1c of 70%, 7.3%~8.4% of fasting and postprandial glucose contribution to half, when HbA1c>8.4% of the contribution to the postprandial glucose, when When HbA1c>8.4% or more, the contribution of fasting blood glucose not only exceeded the value added by postprandial blood glucose, but also increased with the increase of HbA1c level, and when HbA1c>10.2% or more, the contribution of fasting blood glucose reached 70%. Since the effects of fasting and postprandial glucose are different in patients with different glycated hemoglobin levels, this study addresses the differences in the contribution of fasting and postprandial glucose appreciation to different HbA1c. As patients progressed from moderate to severe hyperglycemia, the respective contributions of fasting and postprandial glucose changed progressively, with the contribution of postprandial glucose drift being large below moderate hyperglycemia, and the effect of fasting glucose on HbA1c increasing progressively above moderate hyperglycemia, with fasting glucose demonstrating a more important role with worsening diabetes. This study also suggests that clinicians should individualize the sequence of point glucose therapy and focus on different periods of time according to different levels of HbA1c. Physiologic variation in HbA1c Although HbA1c is the gold standard for long-term glucose monitoring in diabetic patients, and glucose levels are undoubtedly an important determinant of HbA1c, and studies in diabetic populations have shown a strong correlation between HbA1c and prior blood glucose averages, physiologic variation exists among individuals. Mean blood glucose and HbA1c levels measured quarterly in 1441 subjects in the DCCT database were analyzed together with predicted HbA1c (calculated values), with the assumption that if mean blood glucose correlates well with predicted HbA1c, then measured HbA1c levels should differ very little from predicted HbA1c. The difference in HbA1c, referred to as the hemoglobin index (HGI), was obtained by taking the actual measured HbA1c-predicted HbA1c for each patient. The HGI was categorized into three groups: high, medium and low. After 7 years of follow-up, the risk of retinopathy and nephropathy in the high HGI group was three and six times higher than that in the low HGI group, adjusting for mean glucose, age, treatment group, stratification and duration of diabetes mellitus (p<0.001). This suggests that inter-individual physiologic variability in HbA1c is at least as much a predictor of diabetic complications, and that unknown factors are at work in addition to the effect of HbA1c produced by mean blood glucose. In conclusion, the glycemic diagnostic criteria for diabetes mellitus are based on glycemic values that are meaningful for the presence of microvascular disease as a means of determining disease status. However, mild to moderate hyperglycemia lacks obvious symptoms, and long-term monitoring of blood glucose levels is necessary to keep blood glucose in a good range; HbA1c is currently a good indicator of long-term glycemic control, but physiological variations between individuals should be noted. 2005 IDF guidelines for the treatment of diabetes mellitus state that the goal for glycemic control in diabetes mellitus is an HbA1c <6.5%. In areas where HbA1c measurement is not available, spot blood glucose can be used instead. The point glucose equivalent of HbA1c <6.5% is fasting glucose <6.0 mmol/L and 1-2 hours postprandial glucose <8.0 mmol/L. Blood Glucose Meter Current clinical blood glucose meters are easy to operate and provide accurate results. When selecting a glucose meter, one should consider its characteristics and the ease of use for the patient (e.g., vision, non-right-handedness). Instruments may vary in size, the amount of blood required, the speed of measurement, the storage of results, and the price of the instrument and test strips. Some blood glucose meters can take blood from places other than the fingertips, such as the upper arm, forearm, and thigh. However, it is generally recognized that blood taken from the arm does not reflect low and high blood sugar as quickly as blood taken from the fingertips. Alternatively, the fingertips may show changes in blood glucose more quickly than other areas. Glucose meters may have other features such as automatic timing, error codes, signals, and reading of test strip lot numbers for calibration. For patients with visual impairments, some glucose meters have voice prompts or larger displays. The Importance of Accuracy The reliability of a patient's SMBG measurements presents a challenge in managing diabetes. When reporting blood glucose levels, patients may adjust high or low readings to narrow the gap between ideal values. This leads us to educate patients by emphasizing the importance of monitoring blood glucose to maintain near-normal blood glucose on a daily basis. Making patients aware that glucose meters have a memory function can help improve the reliability of SMBG measurements. In a study of intensive treatment for type 1 diabetes, the memory function of glucose meters with computer-assisted analysis was found to improve glycemic control more than the meter-to-diary format. Intensive treatment included monthly glucose measurements, interviews with nurses who monitored glucose control and treatment compliance, and adjustments to the regimen when needed. All patients had been on an insulin pump or four daily insulin injections for 1 year before starting the memory-based glucose meter. Although the frequency of measurements increased from 4.59 to 5.25 times per day, the difference was not significant. However, changes in HbA1c values correlated with the frequency of glucose monitoring. This study confirms that blood glucose readings and systematic interpretation can help patients maintain self-care behaviors toward compliance. Patients should be told to bring a glucose meter to their visit appointments for on-the-spot self-testing to improve their self-measurement techniques and accuracy of measurements, and frequent education on testing techniques can ensure the accuracy of measurements. HbAlc Monitoring HbA1c values represent a combination of fasting and postprandial glucose levels over the past 3 months.The ADA recommends that HbA1c be measured preferably twice a year for patients with diabetes who are in compliance, and four times a year for those who are not in compliance or who have changed their treatment regimen. Instruments that provide rapid HbA1c results can help improve glycemic control. A randomized, prospective, controlled study compared laboratory methods with those that provide immediate results when treated with insulin. Baseline HbA1c was 8.67% and 8.49%, with comparable daily insulin doses and frequency of injections, and at 6 and 12 months, HbA1c was significantly improved in the immediate results group (-0.57% and -0.40%; p<0.01) compared with the control group (-0.11% and -0.19%). Despite the absence of behavior-specific changes, it was found that the frequency of insulin injections increased in the HbA1c immediate outcome group (p<0.001), suggesting that the results of the assay led patients to change their injection regimen. This result supports the hypothesis that rapid use of the results of the assay in clinical treatment would be beneficial in achieving optimal glycemic control. Although HbAlc is a standardized measure of long-term glycemic control, it is not suitable for diabetic patients with shortened red blood cell life spans such as hemoglobinopathies and blood loss. In such cases, the measurement of mean blood glucose or fructosamine levels is a better indicator of glycemic control than the measurement of glycosylated hemoglobin. There is evidence that the response to elevated blood glucose HbAlc varies between individuals and that 62% of this population variation is a genetic effect. Recent data suggest that biological variation in HbA1c values is a predictive risk factor for retinopathy and nephropathy in patients with type 1 diabetes. However, the source of the variation is not known.